Post-emergent refers to a type of herbicide that is applied after weeds have already sprouted and become visible. These products target actively growing weeds, disrupting their growth processes and ultimately leading to their death. Post-emergent herbicides can be selective, affecting only certain types of plants, or non-selective, killing any plant they come into contact with. These herbicides are commonly used in agriculture, landscaping, and home gardens to manage unwanted vegetation. Effective application requires proper timing and conditions, as factors like weather and the specific type of weed can influence the success of the treatment.